import React,{useEffect, useState} from 'react'


 function Child() {

    useEffect(() => {
        console.log('挂载阶段:componentDidMount');
        return () => {
            console.log('卸载阶段:componentWillUnmount')
        }
    },[])
  return (
      <div>
          <h3>Child</h3>
    </div>
  )
}



export default function App(props) {
    const [isShow, setIsShow] = useState(true);
  return (
      <div>
          <button onClick={() => setIsShow(!isShow)}>显示与隐藏</button>
          {
            isShow && <Child/>
          }
    </div>
  )
}
